48 BULLETIN 1022, U. S. DEPARTMENT OF AGRICULTURE. 
SPINACH. 
Owing to the limited quantity of raw material for use, the data 
upon spinach are incomplete. The figures which were obtained, how- 
ever, are considered of sufficient value to warrant their use, and they 
are theretare presented for what they are worth. 
The spinach was gathered fresh from the field, carefully trimmed, 
washed, and then blanched for two minutes in boiling water. It 
was then placed in the test cans, brought to the required uniform 
temperature, and the 
tests begun. 
PRESSURE TESTS. 
Figure 36 shows the 
tests with spinach in 
No. 2 cans, conducted 
-as- with other food 
materials already de- 
scribed. 
The salient features 
PRESSURE IN POUNDS PER SOUARE INCH 
not differ from those 
shown in the tests 
upon corn. As in 
corn, there is a very 
sudden rise in the 
TE USL ee a  Prescure ww cniges a ases 
Fic. 36.—Experimental time-pressure curves for spinach to the sudden expan- 
in No. 2 tin cans, sealed at different uniform tem- : aD ae 
, - sion of the air in th 
peratures and processed for 2 hours at 116° and poe = = 
121° C. Curve for can sealed: A, At 183° C. and head space, after 
processed at 116° C.; B, at 70° C. and processed at Ta es = 
116° C.; 6, at 70° C. and processed at 121° C.; C, at which the Lee 
Shr C! pad processed at 116° Cie ab. Ouse ane. pressure 1S more erad- 
Bs Sager vos eta ual. The continued 
Increase in pressure is due apparently to the liberation of gases. 
In one case this was found to be still taking place at the end of more 
than three hours.- Only one curve is given for cans sealed at low 
temperatures and none at all for the processing temperature of 100° C. 
That great reduction in pressure is obtained, however, by sealing at 
the higher temperatures is shown. 
VACUUM STUDIES. 
The vacuum tests upon spinach, while incomplete, as in the case — 
of the pressure, bring out the following facts clearly: 
(1) The vacuum obtained by sealing the spinach into the can at the desired 
temperature and then cooling immediately always gives a higher vacuum read- 
curves for pressure 
of these curves do 
